The specification of timed Petri net models used by TPN-tools is described in greater detail in Technical Report 9601 which discusses the structure of specifications (i.e., the "input language"), provides several examples of net descriptions, and discusses the internal representation of net models used by the tools.
A brief introduction to event-driven simulation and its implementation in TPN-tools is described in Technical Report 9602. Processing of transition firings, event scheduling and conflict resolutions are discussed in greater detail there and several examples are provided to illustrate the simulation technique.
At present, TPN-tools are intended for analysis of medium-size models. Several improvements and extensions are planned for handling large-size models; more efficient generation of reachable states, iterative solutions of stationary probabilities, or use of distributed systems for simulation as well as reachability analyses are examples of such improvements. Moreover, a composition of large models from simpler ones, or a hierarchical representation of complex models, is needed for efficient analysis of models containing hundreds or more elements.
The specification language is rather "low-level" which means that the model description is at a rather detailed level. It is anticipated that a more convenient graphical user interface, of the type used by GreatSPN [Ch92] or DSPNexpress [Li92], will be developed (or adopted) at some later time.
For colored net models, the current version of model specifications requires all occurrences to be described explicitly. A more convenient (and flexible) approach allows to use symbolic variables and implied rather than explicit occurrences. All such features can easily be added to the TPN-tools collection.
A c k n o w l e d g e m e n t
Software tools for analysis of timed Petri net models were developed over many years, using direct and indirect contributions of many colleagues and students. All these contributions, rather difficult to trace and identify because of countless software modifications, redesigns and extensions, are gratefully acknowledged. The Natural Sciences and Engineering Research Council of Canada partially supports this research through Research Grant OGP-8222.
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